Bulk-modified modified screen-printing carbon electrodes with both lactate oxidase (LOD) and horseradish peroxide (HRP) for the determination of L-lactate in flow injection analysis mode

A screen-printed carbon electrode modified with both HRP and LOD (SPCE–HRP/LOD) has been developed for the determination of l-lactate concentration in real samples. The resulting SPCE–HRP/LOD was prepared in a one-step procedure, and was then optimised as an amperometric biosensor operating at 0, −100] mV versus Ag/AgCl for l-lactate determination in flow injection mode. A significant improvement in the reproducibility (coefficient variation of about 10%) of the preparation of the biosensors was obtained when graphite powder was modified with LOD in the presence of HRP previously oxidised by periodate ion (IO₄⁻). Optimisation studies were performed by examining the effects of LOD loading, periodation step and rate of the binder on analytical performances of SPCE–HRP/LOD. The sensitivity of the optimised SPCE–HRP/LOD to l-lactate was 0.84 nA L μmol⁻¹ in a detection range between 10 and 180 μMol. The possibility of using the developed biosensor to determine l-lactate concentrations in various dairy products was also evaluated.